• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.443-446
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• 2009

In this paper, an accurate ray-tracing based visual analysis method of lenticular 3D liquid liquid crystal display (LCDs) and some analysis results are presented. In the developed method, the geometric optics analysis is performed on the single 3D unit pixel of 3D lenticular LCD. It is shown that the display characteristics of 3D lenticular LCD panels of arbitrary size can be evaluated through the 3D unit pixel analysis. The analysis results of a few representative structures of 3D lenticular LCDs are compared.

• Carbon letters
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• 제14권2호
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• pp.89-93
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• 2013

Size-sorted graphene nanoplatelets are highly desired for fundamental research and technological applications of graphene. Here we show a facile approach for fabricating size-sorted graphene oxide (GO) nanoplatelets by a simple centrifugal method using different dispersion solvents. We found that the small-sized GO nanoplatelets were more effectively separated when dispersed in water or dimethylformamide (DMF) than in an alkali aqueous solution. After several iterations of the centrifugation, the sizes of GO in the supernatant solution were mostly several micrometers. We found that the GO area was not strongly correlated with the C-O content of the GO dispersed in water. However, the size-sorted GO nanoplatelets in DMF showed different C-O content, since DMF can reduce GO nanoplatelets during exfoliation and centrifugation processes.

• 대한수학회지
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• 제44권6호
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• pp.1479-1503
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• 2007

In this paper, we study a strong k-deformation retract derived from a relative k-homotopy and investigate its properties in relation to both a k-homotopic thinning and the k-fundamental group. Moreover, we show that the k-fundamental group of a wedge product of closed k-curves not k-contractible is a free group by the use of some properties of both a strong k-deformation retract and a digital covering. Finally, we write an algorithm for calculating the k-fundamental group of a dosed k-curve by the use of a k-homotopic thinning.

• 대한수학회보
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• 제46권5호
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• pp.823-833
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• 2009

It is well-known that if a convex hyperbolic polygon is constructed as a fundamental domain for a subgroup of the modular group, then its translates by the group elements form a locally finite tessellation and its side-pairing transformations form a system of generators for the group. Such hyperbolically convex polygons can be obtained by using Dirichlet's and Ford's polygon constructions. Another method of obtaining a fundamental domain for subgroups of the modular group is through the use of a right coset decomposition and we call such domains standard fundamental domains. In this paper we give subgroups of the modular group which do not have hyperbolically convex standard fundamental domain containing only inequivalent cusps.

• 호남수학학술지
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• 제25권1호
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• pp.153-162
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• 2003

Recently, the generalized digital $(k_{0},\;k_{1})$-continuity and its properties are investigated. Furthermore, the k-type digital fundamental group for digital image has been studies with the generalized k-adjacencies. The main goal of this paper is to find some properties of the k-type digital fundamental group of Boxer and to investigate some properties of minimal simple closed k-curves with relation to their embedding into some spaces in ${\mathbb{Z}}^n(2{\leq}n{\leq}3)$.

• 대한수학회논문집
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• 제11권3호
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• pp.825-829
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• 1996

We prove that if G is the fundamental group of a closed surface or a Seifert fibered space and K is a finitely generated subgroup of G, and if for any element g in G there exists an integer $n_g$ such that $g^{n_g}$ belongs to K, then K is of finite index in G.

• 기본간호학회지
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• 제5권1호
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• pp.81-93
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• 1998

The effectiveness of medication video tapes in teaching fundamental nursing skills was investigated using experimental research methodology. Data was collected from 153 students attending fundamental nursing practice classes of two junior colleges and two universities. The subjects were randomly assigned to two groups, one was an experimental group of 74 subjects and the other was a control group of 79 subjects. The independent variable was learning type and the dependent variables were the degree of knowledge achievement and nursing skills achievement regarding medication. The research hypotheses of this study were as follows : 1) There will be a significant difference between the experimental group and the control group in the degree of knowledge achievement about medication. 2) There will be a significant difference between the experimental group and the control group in the nursing skills achievement about medication. The data was analyzed with the SPSSWIN program and the t-test, number of subjects and percentiles were then examined. The findings of this study are as follows : 1) There was a significant difference between the experimental group and the control group in the knowledge achievement about medication using P<.05. 2) There was no significant difference between the experimental group and the control group in the nursing skill achievement about medication using P<.05. 3) This study suggests that medication video tapes in the education of fundamental nursing skills are effective for knowledge achievement. As a result, medication video tapes can be effectively utilized for the education of nursing skills regarding medication.

• 호남수학학술지
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• 제36권3호
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• pp.695-706
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• 2014

Various properties of digital covering spaces have been substantially used in studying digital homotopic properties of digital images. In particular, these are so related to the study of a digital fundamental group, a classification of digital images, an automorphism group of a digital covering space and so forth. The goal of the present paper, as a survey article, to speak out utility of digital covering theory. Besides, the present paper recalls that the papers [1, 4, 30] took their own approaches into the study of a digital fundamental group. For instance, they consider the digital fundamental group of the special digital image (X, 4), where X := $SC^{2,8}_4$ which is a simple closed 4-curve with eight elements in $Z^2$, as a group which is isomorphic to an infinite cyclic group such as (Z, +). In spite of this approach, they could not propose any digital topological tools to get the result. Namely, the papers [4, 30] consider a simple closed 4 or 8-curve to be a kind of simple closed curve from the viewpoint of a Hausdorff topological structure, i.e. a continuous analogue induced by an algebraic topological approach. However, in digital topology we need to develop a digital topological tool to calculate a digital fundamental group of a given digital space. Finally, the paper [9] firstly developed the notion of a digital covering space and further, the advanced and simplified version was proposed in [21]. Thus the present paper refers the history and the process of calculating a digital fundamental group by using various tools and some utilities of digital covering spaces. Furthermore, we deal with some parts of the preprint [11] which were not published in a journal (see Theorems 4.3 and 4.4). Finally, the paper suggests an efficient process of the calculation of digital fundamental groups of digital images.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
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• pp.51-59
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• 2006

서해안 조간대에서 24 channel 탐사기로 획득한 표면파 자료의 위상속도와 군속도를 구한다음, 이를 역산하여 그 결과를 비교하였다. 위상속도의 분산곡선은 tau-p stacking 방법에 의하여, 군속도의 분산곡선은 wavelet analysis와 Multiple Filtering Technique의 두가지 방법을 사용하여 구하였다. 위상속도의 오차가 군속도의 오차보다 더 큰 것을 확인하였다. 군속도의 경우, wavelet analysis가 Multiple Filtering Technique 보다 fundamental mode와 higher mode를 구분하는데 더 효과적이었다. 역산결과, 군속도의 fundamental mode와 1st higher mode 를 동시에 사용했을 때, 공간적 해상도가 가장 좋았다. 이연구는 천부 지반의 S파 속도 구조를 구하는데, 군속도의 higher mode를 포함한 군속도 분산곡선을 사용하는 것이 효과적임을 시사한다.

• 대한수학회보
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• 제48권1호
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• pp.129-140
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• 2011

The aim of this paper is to study the structure of the fundamental group of a closed oriented Riemannian manifold with positive scalar curvature. To be more precise, let M be a closed oriented Riemannian manifold of dimension n (4 $\leq$ n $\leq$ 7) with positive scalar curvature and non-trivial first Betti number, and let be $\alpha$ non-trivial codimension one homology class in $H_{n-1}$(M;$\mathbb{R}$). Then it is known as in [8] that there exists a closed embedded hypersurface $N_{\alpha}$ of M representing $\alpha$ of minimum volume, compared with all other closed hypersurfaces in the homology class. Our main result is to show that the fundamental group ${\pi}_1(N_{\alpha})$ is always virtually free. In particular, this gives rise to a new obstruction to the existence of a metric of positive scalar curvature.